This is a proposal to study the articulatory underpinnings of speech intelligibility deficits in the neurogenic speech disorders associated with Parkinson disease (PD) and amyotrophic lateral sclerosis (ALS). The proposed work uses x-ray microbeam (articulatory kinematic), speech acoustic, and speech intelligibility measures to address a major descriptive need, as well as a clinically- and theoretically-relevant hypothesis. Very little is known about lingual behavior in dysarthrias, and what is known about labial and mandibular behavior in dysarthria is confined to a limited type of speech material and measurement strategy. The present proposal includes a variety of speech materials to allow a broad characterization of articulatory kinematics (and the speech acoustic and intelligibility results of those motions) for speech production behavior. One way in which the articulatory kinematics will be characterized is by means of a measure of articulatory working space (i.e., parameterization of ranges). A central hypothesis is that there is a relationship between the size of these articulatory working spaces defined kinematically on the one hand, and the size of the acoustic working spaces and speech intelligibility on the other hand. Specifically, we test the idea, in several ways, that articulatory reduction is the primary segmental reason for reduced intelligibility in persons with ALS and PD. The hypothesis has been shown in the first funding period to hold across speakers within each of the two disorder groups, and will now be studied within neurologically-impaired speakers who are asked to control speech variables such as rate, loudness, and clarity so as to create variation in the magnitude of articulatory movements. Another major area of study is to identify the nature and possible disorder of articulatory coordination in dysarthria. Dysarthria is often described as having a prominent component of articulatory dyscoordination, but the small amount of relevant data that exist have not revealed the kind of frank coordination disorder that might be expected from typical textbook descriptions. A finding from the first funding cycle of small abnormalities in the degree of coordination, but an essentially-normal 'form' of coordination for a particular phonetic sequence will be followed up with analyses of additional sequences, as well as with the inclusion of analyses of articulatory scale in these patients and in neurologically-healthy controls. ? ?
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